Security and authentication systems generally require users to explicitly recall user memories or learning, for example, passwords or identification numbers, and to consciously enter such information into the validating system. These authentication tactics have an inverse relationship between security and usability. For instance, making passwords more complex increases security at the expense of an increased cognitive burden on the user. Conversely, making passwords simpler to ease the cognitive burden on the user comes at the expense of overall security. Weaknesses in human memory also present limitations on possible security passwords and/or decrease the effectiveness of systems relying on conscious user memories to gain system access.